1. Field of the Invention
The present invention relates to orthopedic components, and, particularly, to intramedullary nails.
2. Brief Description of the Related Art
Intramedullary nails may be used to align and stabilize fractures of a long bone. For example, in a fractured femur, an intramedullary nail may be inserted into the intramedullary canal of the femur and positioned to extend across the fracture line of the femur. Then, screws or other securement devices may be inserted within bores formed in the intramedullary nail to secure the opposing portions of the fractured femur together.
If the head of a long bone, such as the head of a femur, has fractured, lag screws may be inserted into transverse bores formed in an intramedullary nail to extend into the head of the long bone to compress the opposing portions of the fractured bone together. In this arrangement, the lag screw extends through a lag screw hole in the intramedullary nail and applies torque to the intramedullary nail. Because of the lag screw hole, the applied torque creates higher stress concentrations in the intramedullary nail near the lag screw hole.
United States Patent Application Publication No. US 2005/0149024 to Ferrante et al. describes an intramedullary nail that attempts to reduce stress in the intramedullary nail by increasing the size of a portion of the nail. As described in Ferrante et al., additional material is provided on a lateral side of the intramedullary nail. As shown in FIG. 1 of Ferrante et al., this additional material extends from a location distal of the lag screw hole to a proximal end of the intramedullary nail. During preparation of the femur to receive this intramedullary nail, a surgeon must remove additional bone along a substantial extent of the intramedullary canal to accommodate the additional material. Further, the surgeon must prepare a non-circular bore in the femur to receive the intramedullary nail of Ferrante et al.